Convert from QByteArray to array of double

Question

I have an array of double:

QVector<double> Y(count);

I need to pack it to QByteArray to send via Ethernet.

So I did it. It was not too hard:

QByteArray line;
line.clear();
line.append(QByteArray::fromRawData(reinterpret_cast<const char*>(Y.data()),
count*sizeof(double)));

I try use this code to unpack the data from QByteArray recv :

QVector<double> data((line.size())/sizeof(double));
QByteArray dou(sizeof(double),0x0);
for(int i = 0; i<data.count(); i++){
    dou = recv.mid(i*sizeof(double),sizeof(double));
    data[i] = *reinterpret_cast<const double*>(dou.data());
    dou.clear();
}

But I don’t like it. I want to find out elegant way to unpack from QByteArray to QVector<double> Can you help me?

Answer 1

you can use a QDataStream which will encode the data in binary in a specific format. (more specifically first the number of items (int32) and then each item)

QVector has overloads for the stream operators

QByteArray line;
QDataStream stream(&line, QIODevice::WriteOnly);
stream << y;

and to read:

QVector<double> data;
QDataStream stream(line);
stream >> data;

Answer 2

The common practice is to serialize the data as a text. This will make your server and client portable. Sending a binary data over the network is not a good idea. You can create your own text protocol, or use the existing one (like Google Protocol Buffers).